According to this author, in such individuals there exist anatomical anomalies which, by an error of Nature, consist in a distribution to the rectum of the nerves intended for the genitals; so that only in this situation the lustful sensation is aroused which otherwise results from stimulation of the genitals. But how does this author, in other ways so acute, explain the great majority of cases, where pederasty is abhorred by those affected with contrary sexual feeling? Besides, Nature never makes such leaps. Mantegazza rests his hypothesis upon the statements of an acquaintance, a celebrated writer, who assured him that he was not sure that he took a greater pleasure in coitus than in defecation! Allowing the correctness of his experience, still it would only prove that the man was sexually abnormal, and that his pleasure in coitus was reduced to a minimum. An explanation of congenital contrary sexual feeling may perhaps be found in the fact that it represents a peculiarity bred in descendants, but arising in ancestry. The hereditary factor might be an _acquired_ abnormal inclination for the same sex in the ancestors (_v. infra_), found fixed as a congenital abnormal manifestation in the descendants. Since, according to experience, acquired physical and mental peculiarities, not simply improvements, but essentially defects, are transmitted, this hypothesis becomes tenable. Since individuals affected with contrary sexual feeling not infrequently beget children,—at least, they are not absolutely impotent (women never are),—a transmission to descendants is possible. This supposition is decidedly favored by Case 124, in which the eight-year-old daughter of an individual affected with contrary sexual feeling, practiced mutual masturbation—a sexual act—at an age which permits the presumption of contrary sexual feeling. No less significant is the communication made to me by a young man of twenty-six, who belongs to the third group of contrary sexuality. He knew with certainty that his father, who had died some years before, was also subject to contrary sexuality. An informant assured me, at least, that he knew many other men with whom his father had sustained “relations.” Whether, in the case of the father, it was an acquired or a congenital contrary sexual instinct, and to what group he belonged, could not be ascertained. The foregoing hypothesis seems the more plausible, when it is considered that the first three degrees of congenital contrary sexual instinct correspond exactly with the developmental stages which are discoverable in the development of the acquired anomaly. One, therefore, feels inclined to designate the various degrees of congenital contrary sexual instinct as various degrees of an hereditarily-induced sexual anomaly, acquired from the progenitors or otherwise developed. Here, too, the law of progressive heredity must be taken into consideration.